#include <bits/stdc++.h>
using namespace std;

int main() {
    int a, b;
    cin >> a >> b;
    if (2.00 * a - 3.00 * b + a * b - 6.00 == 0) {
        cout << "Data error\n";
        return 0;
    }
    printf("%.2f\n", (3.00 * (2.00 * a - 3.00 * b) - a * (-5.00 + 3.00 * b) + b * (-4.00 * a - 5.00)) /
                     (2.00 * a - 3.00 * b + a * b - 6.00));
    return 0;
}